As a continuation of previous projects on clinical, pathological, and epidemiologic surveillance of Guamanian amyotrophic lateral sclerosis (ALS) and Parkinsonism-dementia (PD) in the Marianas Islands, identified survivors, including suspects, in the NINDS Registry as of January 1, 1983, were followed at intervals of six months for detailed clinical descriptions of patterns of progression, by a qualified neurologist. The patients still alive have entered a chronic state and final exams were completed in the fall of 1988. As these patients expire, attempts will be made to obtain the appropriate pathologic material for examination by various neuropathologists around the world. All attempts to examine this material should be made because of the uniqueness of these patients. The prevalence survey of three southern Guamanian villages to determine the current prevalence of ALS/PDC was completed in 1988. As this is a transitional society, dietarily and culturally since WW-II, a simultaneous survey for other major neurologic diseases and major diseases of aging populations was also performed. A chart review study using the NINDS Guam registry for ALS/PDC for the period 1944-85 was performed. Downward trends in age-adjusted incidence rates and upward trends in age of onset were seen for both sexes. Since 1980, new cases occurred only among persons over 50 years of age, whereas younger age at onset had been noted in the past.